Casting thin strip and delivery nozzle therefor

ABSTRACT

A method of casting metal strip and equipment therefor where an elongated metal delivery nozzle extending along in a continuous caster with at least one segment having a main portion adapted to deliver molten metal in the casting pool above the nip along the metal delivery nozzle and an end portion adjacent side dams having a reservoir portion with first and second passages adapted to deliver molten metal into a molten metal pool adjacent the side dams while shells are forming on the casting rolls. The first passages are adapted to deliver molten metal shallowly into the casting pool adjacent the side dams, and the second passages adapted to deliver molten metal deeper into the casting pool than the first passages adjacent the side dams to inhibit formation of skulls during the formation of the cast strip during a casting campaign.

RELATED APPLICATION

This application claims priority to and the benefit of U.S. ProvisionalPatent Application No. 61/483,405, filed May 6, 2011, the disclosure ofwhich is incorporated herein by reference.

BACKGROUND AND SUMMARY OF THE INVENTION

This invention relates to making thin strip and, more particularly,casting of thin strip by a twin roll caster.

It is known to cast metal strip by continuous casting in a twin rollcaster. Molten metal is introduced between a pair of counter-rotatinghorizontal casting rolls which are cooled so that metal shells solidifyon the moving roll surfaces and are brought together at the nip betweenthe casting rolls to produce a solidified strip product delivereddownwardly from the nip. The term “nip” is used herein to refer to thegeneral region at which the rolls are closest together. The molten metalmay be poured from a ladle into a smaller vessel or tundish/distributor,from which it flows through a metal delivery nozzle located above thenip, which directs the molten metal to form a casting pool supported onthe casting surfaces of the rolls above the nip. This casting pool maybe confined at the ends of the casting rolls by side plates or dams heldin sliding engagement adjacent the ends of the rolls.

In casting thin strip by twin roll casting, the metal delivery nozzlesreceive molten metal from the movable tundish and deposit the moltenmetal in the casting pool in a desired flow pattern. Previously, variousdesigns have been proposed for delivery nozzles involving a lowerportion submerged in the casting pool during a casting campaign, andhaving side openings through which the molten metal is capable offlowing laterally into the casting pool outwardly toward the castingsurfaces of the rolls. Examples of such metal delivery nozzles aredisclosed in Japanese Patent No. 09-103855 and U.S. Pat. No. 6,012,508.In prior art metal delivery nozzles, there has been a tendency toproduce thin cast strip that contains defects from uneven solidificationat the chilled casting surfaces of the rolls.

In the past, the formation of pieces of solid metal known as “skulls” inthe casting pool in the vicinity of the confining side plates or damshave been observed. These skulls become “snake-eggs” in the cast stripwhen swallowed and passed through the nip into the cast strip. The rateof heat loss from the casting pool is higher near the interface betweenside dams and the casting rolls (called the “triple point region”) dueto conductive heat transfer through the side dams to the casting rollends. This localized heat loss near the side dams has a tendency to formskulls of solid metal in that region, which can grow to a considerablesize and fall between the casting rolls and cause defects in the caststrip. An increased flow of molten metal to these regions near the sidedams and meniscus of the casting pool have been provided by separatedirect flows of molten metal to these regions. Examples of suchproposals may be seen in U.S. Pat. No. 4,694,887 and in U.S. Pat. No.5,221,511. Increased heat input to these regions has inhibited formationof skulls.

Nevertheless, we have continued to observe skulls in the triple pointregion and also deeper into the casting pool adjacent the side dams. Itwas thought that such formation of skulls was near the meniscus of thecasting pool as the shells were initially formed. We have now discoveredthat such skulls can also form deeper in the casting pool as the shellscontinue to form as the shells move toward the nip. We have found thatthe formation of skulls can be substantially reduced by providingdifferent flows through first and second passages of a reservoir portionof the metal delivery nozzle, the first passages delivering the moltenmetal shallowly into the casting pool adjacent the side dams and thesecond passages delivering the molten metal deeper into the casting pooladjacent the side dams while shells are formed in the casting rolls.

The present invention provides a method of casting thin strip with thedelivery nozzle and an improved delivery nozzle therefor. Disclosed is amethod of casting metal strip comprising:

-   -   (a) assembling a pair of casting rolls laterally disposed to        form a nip between them and between side dams adapted to        maintain a molten metal pool supported by the casting rolls,    -   (b) assembling an elongated metal delivery nozzle extending        along and above the nip with at least one segment having a main        portion adapted to deliver molten metal in the casting pool        along the metal delivery nozzle and an end portion adjacent side        dams having a reservoir portion having first and second passages        adapted to deliver molten metal into a molten metal pool        adjacent the side dams while shells are forming on the casting        rolls, the first passages adapted to deliver molten metal        shallowly into the casting pool adjacent the side dams and the        second passages adapted to deliver molten metal deeper into the        casting pool than the first passages adjacent the side dams,    -   (c) introducing molten metal through the elongated metal        delivery nozzle to form a casting pool of molten metal supported        on the casting rolls above the nip, and through the first and        second passages in the reservoir portion in the end portions        into the casting pool, and    -   (d) counter rotating the casting rolls to deliver cast strip        downwardly from the nip.

The first and second passages of the reservoir portion may besubstantially parallel. The first and second passages of the reservoirportion may be between 5 and 30 millimeters apart, between edge portionsof the passages. The first and second passages themselves may begenerally 7 to 12 millimeters in diameter, and the first and secondpassages may be of different diameter as desired to deliver the moltenmetal into the casting pool at the desired location adjacent the sidedams.

The method may be provided with a reservoir portion in the end portionof each segment having longitudinally extending weirs adjacent the sidewalls of the inner trough adapted to allow molten metal to flow over theweirs between the reservoir portion and the main portion of the metaldelivery nozzle.

The method of casting metal strip may be also provided with dual firstand second passages in each reservoir portion of the metal deliverynozzle adjacent the side dams. In this embodiment the first and secondpassages may be provided in pairs on both sides of the side dams nearthe casting rolls. Again, the first and second passages of the reservoirportion may be between 5 and 30 millimeters apart, measured between nearwall portions of the passages. The first and second passages themselvesagain may be generally 7 to 12 millimeters in diameter, and the firstand second passages may be of different diameter as desired to deliverthe molten metal into the casting pool at the desired locations.

Also disclosed is a metal delivery apparatus for casting metal stripcomprising at least one elongated segment having a main portion adaptedto deliver molten metal in the casting pool along the metal deliverynozzle and an end portion adjacent side dams having a reservoir portionhaving first and second passages adapted to deliver molten metal into amolten metal pool adjacent the side dams while shells are forming on thecasting rolls, the first passages adapted to deliver molten metalshallowly into the casting pool adjacent the side dams and the secondpassages adapted to deliver molten metal deeper into the casting poolthan the first passages adjacent the side dams.

The first and second passages of the reservoir portion of the metaldelivery nozzle may be between 5 and 30 millimeters apart, measuredbetween near wall portions of the passages. The first and secondpassages of the reservoir portion of the metal delivery nozzle may ormay not be substantially parallel. In any case, the first and secondpassages of the metal delivery nozzle may be generally 7 to 12millimeters in diameter, and the first and second passages may be ofdifferent diameter as desired to deliver the molten metal into thecasting pool at the desired locations adjacent the side dams.

The metal delivery apparatus for casting metal strip may be providedwith a reservoir portion in the end portion of each segment havinglongitudinally extending weirs adjacent the side walls of the innertrough adapted to allow molten metal to flow over the weirs between thereservoir portion and the main portion of the metal delivery apparatus.

The metal delivery apparatus for casting metal strip may be alsoprovided with dual first and second passages in each reservoir portionof the metal delivery nozzle adjacent the side dams. In this embodiment,the first and second passages may be provided in pairs adjacent bothsides of the side dams near the casting rolls. Again, the parts of thefirst and second passages of the reservoir portion may be between 5 and30 millimeters apart, between edge portions of the passages. The firstand second passages of the reservoir portion of the metal deliverynozzle may be or may not be substantially parallel as desired. The firstand second passages of the metal delivery apparatus also may begenerally 7 to 12 millimeters in diameter, and the first and secondpassages may be of different diameter as desired to deliver the moltenmetal into the casting pool at the desired location.

The metal delivery apparatus for casting metal strip may have dual firstand second passages in each reservoir portion of the metal deliverynozzle. The first and second passages of the reservoir portion also maybe shaped to control the molten metal flow through the passages byincreasing or decreasing the velocity of molten metal through thepassage, and, in turn, control the kinetic energy of the molten metalexiting the passage to direct the molten metal shallow or deep into thecasting pool as explained in more detail below.

Various aspects of the invention will be apparent from the followingdetailed description, drawings, and claims.

BRIEF DESCRIPTION OF THE DRAWINGS

The invention is described in more detail in reference to theaccompanying drawings in which:

FIG. 1 a illustrates a cross-sectional end view of a portion of twinroll strip caster with an assembled metal delivery nozzle;

FIG. 1 b is an enlarged view of a portion of twin roll strip castersimilar to FIG. 1 a except showing a trough with a concave uppersurface;

FIG. 2 is a plan view of a segment of a metal delivery nozzle for use inthe twin roll caster shown in FIG. 1 a;

FIG. 3 is a cross-sectional side view taken along line 3-3 of thesegment of the metal delivery nozzle shown in FIG. 2;

FIG. 4 is a cross-sectional side view taken along line 4-4 of thesegment of the metal delivery nozzle shown in FIG. 2;

FIG. 5 is a cross-sectional transverse taken along line 5-5 of thesegment of the metal delivery nozzle shown in FIG. 2;

FIG. 6 is a cross-section transverse view of an alternative embodimentof the segment of a metal delivery nozzle shown in FIG. 5;

FIG. 7 is a cross-sectional transverse view of an alternative embodimentof the segment of a metal delivery nozzle shown in FIG. 5;

FIG. 8 is a cross-sectional side view similar to FIG. 3 of analternative embodiment of a metal delivery nozzle for use in the twinroll caster shown in FIG. 1;

FIG. 9 is a plan view of a segment of an alternative metal deliverynozzle for use in the twin roll caster shown in FIG. 1;

FIG. 10 is a cross-sectional side view of a segment of anotheralternative metal delivery nozzle for use in the twin roll caster shownin FIG. 1;

DETAILED DESCRIPTION OF THE INVENTION

Referring to FIGS. la and lb, the metal strip casting apparatus 2includes a metal delivery nozzle 10 located below a tundish 4 and abovea pair of casting rolls 6. The casting rolls 6 are laterally positionedwith a nip 9 formed between them. The tundish 4 receives molten metalfrom a ladle (not shown) and delivers the molten metal to a deliverynozzle 10. A shroud 5 may extend from the tundish 4 and into thedelivery nozzle 10, for the purpose of transferring molten metal intothe delivery nozzle 10. In the alternative, the tundish 4 may transfermolten metal to the delivery nozzle 10 via a hole in the bottom of thetundish 4. Below and around the lower portions of the delivery nozzle10, a casting pool 8 having a surface 8A is formed and supported on thecasting surfaces 7 of the casting rolls 6 adjacent the nip 9. Thecasting pool 8 is constrained at the ends of the casting rolls 6 andside dams or plates (not shown) positioned against the ends of thecasting rolls. The side dams and their location in relation to thecasting rolls 6 and the casting pool 8 are described, for example, inU.S. Pat. No. 7,556,084 granted Jul. 7, 2009, and in United StatesPublication No. 2009/0283240 published Nov. 19, 2009, which areincorporated herein by reference. The delivery nozzle 10 controls moltenmetal flow through passages 16 into the casting pool 8. Generally, thedelivery nozzle 10 extends into the casting pool 8 during the castingcampaign as shown in FIGS. 1 a and 1 b. Also, as shown in FIG. 1 a, gascontrol apparatus 3 is provided to maintain a gas seal 11 with thecasting surfaces 7 of the casting rolls 6 and to maintain an inertatmosphere of nitrogen and/or argon above the casting pool 8 by blowingsuch gas through the passageways 12 in the gas control apparatus 3.

Referring to FIG. 2, the delivery nozzle 10 comprises two segments 13(one shown), with each delivery nozzle segment 13 having opposing sidewalls 15 and an upward opening inner trough 14, which extend lengthwisealong the segment 13 in the longitudinal direction of the deliverynozzle 10. In this embodiment, the side walls 15 are joined to the innertrough 14 to form shoulder portions 30, and the passages 16 are in theform of holes 31 extending through the shoulder portions 30 along eachside of the inner trough 14. The molten metal flows from the innertrough 14 through the holes 31 to the side outlets 20. In thisembodiment, the shoulder portions 30 provides the structural support tothe delivery nozzle segment 13 when loaded with molten metal during acasting campaign. As a result, the flow of molten metal from the sideoutlets 20 into the casting pool 8 can be provided laterally more evenlyalong the delivery nozzle segment 13.

The pair of delivery nozzle segments 13 may be assembled lengthwise withthe end walls 19, in abutting relation, and end walls 18 forming theends of delivery nozzle 10. Alternatively, delivery nozzle 10 maycomprise a single delivery nozzle segment 13, or more than two segments13, that include all the features of, and effectively functions as theassembled pair of segments 13 as described herein. Each delivery nozzlesegment 13 may be made of any refractory material, such as aluminagraphite. As shown in FIG. 1, each delivery nozzle segment 13 includesmounting flanges 27 that extend outward from side walls 15, eithercontinuously (as shown in FIG. 2) or, intermittently, as desired, tomount delivery nozzle segments 13 assembled forming the delivery nozzle10 of the casting apparatus 2.

In operation, molten metal is poured through a shroud 5 into the innertrough 14 of mounted delivery nozzle segments 13. Several shrouds 5 maybe provided along the length of the delivery nozzle segments 13. Themolten metal flows from the inner trough 14 into and through passages 16into the side outlets 20. The side outlets 20 direct the flow of moltenmetal to discharge the molten metal laterally into the casting pool 8 inthe direction of the meniscus between the surface 8A of the casting pool8 and the casting surfaces 7 of the casting rolls 6. Since the passages16 and side outlets 20 extend along both sides of the delivery nozzlesegments 13, a relatively uniform flow of molten metal can be providedalong the length of the metal delivery nozzle segments 13. Also, note,as shown, in FIG. 3, the inner trough 14 of each delivery nozzle segment13 may extend into the end portions 18 underneath a reservoir 24(described below) to further extend the relatively uniform flow ofmolten metal into the casting pool 8 along the length of the segment 13.

Referring to FIGS. 2 and 5, the assembly of the reservoir 24 is shown atthe end portion 18 of the delivery nozzle segment 13 adjacent the endsof the casting rolls 6. The region of casting pool 8 below the reservoir24 at the end portion 18 near the intersection of the casting rolls 6and the side dams is the area where skulls are more likely to formbecause of the different heat gradient adjacent a side dam. Tocompensate, molten metal is directed through first passages 22 andsecond passages 23 from the reservoir 24, which is positioned transverseto the end portion 18 of the delivery nozzle segment 13 as shown inFIGS. 2 and 5. The shape of the reservoir 24 is shown in FIGS. 2, 3, and5, with a bottom portion 26 shaped to cause the molten metal to flowinto first passages 22 and second passages 23. A weir 25 is alsoprovided in the segment 13 to separate the flow of molten metal in thereservoir 24 providing a constant head while allowing the flow of moltenmetal from the inner trough 14 concurrently into the passages 16 in themain body of the metal delivery nozzle 10.

As shown in FIG. 5, the first passages 22 and second passages 23 areprovided slanted to deliver the molten metal into this point areaadjacent the side dams. The first passages 22 are adapted to delivermolten metal shallowly into the casting pool 8 adjacent the side dams,and the second passages 23 are adapted to deliver molten metal deeperinto the casting pool 8 than the first passages 22 adjacent the sidedams, while allowing shells to form on the casting surfaces 7 of thecasting rolls 6 without substantial washing by the molten metal fromfirst and second passages 22 and 23, respectively, during a castingcampaign. The first passages 22 and the second passages 23 may bebetween 5 and 30 millimeters apart between near wall portions of thepassages as shown in FIG. 5. The first passages 22 and the secondpassages 23 may also be substantially parallel. The first and secondpassages 22 and 23, respectively, may be between 7 to 12 millimeters indiameter, and the first and second passages may be of differentdiameter, as desired, to deliver the molten metal into the casting pool8 at the desired location as the shells move through and are formed inthe casting pool 8. Also, the first and second passages 22 and 23,respectively, may be provided in pairs on both sides of the side damsnear the casting rolls as shown in FIG. 5.

Referring to FIG. 6, an alternative embodiment of the reservoir 24 of adelivery nozzle segment 13 is shown that is otherwise the same as thatshown in FIG. 1 a. The first passages 22 and the second passages 23 areprovided slanted to deliver the molten metal into the desired areaadjacent the side dams. The first passages 22 are adapted to delivermolten metal shallowly into the casting pool 8 adjacent the side dams,and the second passages 23 are adapted to deliver molten metal deeperinto the casting pool 8 than the first passages 22 adjacent the sidedams, while allowing shells to form on the casting surfaces 7 of thecasting rolls 6 without substantial washing by the molten metal from thefirst and second passages 22 and 23, respectively, during a castingcampaign. In FIG. 6, the first passages 22 are shown having an entryport 35 and an exit port 36 and the second passages 23 are shown havingan entry port 37 and an exit port 38. The first passages 22 are shapedso that the entry port 35 has a smaller diameter than the exit port 36.The exit port 36 having a larger diameter than the entry port 35increases the cross-sectional area for the molten metal as it travelsthrough the first passages 22 and, in turn, reduces the velocity of themolten metal. Thus, the kinetic energy of the molten metal exiting thefirst passages 22 at exit port 36 is reduced and the molten metal isdirected into the shallow part of the casting pool 8 near the regionadjacent the side dams, inhibiting the washing of shells from thecasting roll surface 7, allowing the shells to form and develop duringcasting.

Alternatively or in addition, the second passages 23 are shaped with thepassage 23 at entry port 37 having a larger diameter than the exit port38. The exit port 38 having a smaller diameter than the entry port 37reduces the cross-sectional area for the molten metal as it travelsthrough the second passages 23 and causes the velocity of the moltenmetal to increase as it flows through the second passages 23. Thus, thekinetic energy of the molten metal exiting the second passages 23 at theexit port 38 is increased allowing the molten metal to travel deeperinto the casting pool 8 adjacent the side dam as compared to the moltenmetal flow from the first passages 22. The molten metal is directeddeeper into the casting pool 8 by the second passages 23 and inhibitsthe formation of skulls.

Referring to FIG. 7, an alternative embodiment of the reservoir 24 ofthe delivery nozzle segment 13 is shown that is otherwise the same asthat shown in FIGS. 1 a, 1 b, and 5. The shape of the weir 25 allows theflow of molten metal into the reservoir 24 to impinge on the floor 27,and then flow outwardly and through passages 22 and 23, respectively,into the casting pool adjacent the side dams. The part 28 of thereservoir 24 between passages 22 and 23, respectively, and the outerportion 29 of the reservoir 24 are shaped to provide the desired flowand flow direction to the molten metal through first passages 22shallowly into the casting pool 8 adjacent the side dams and through thesecond passages 23 adapted to deliver molten metal deeper into thecasting pool 8 than the first passages 22 adjacent the side dams, whileallowing shells to form on the casting surfaces 7 of the casting rolls 6without substantial washing by the molten metal from first and secondpassages 22′ and 23′, respectively. This embodiment allows theferrostatic head of molten metal in the reservoir 24 to be controlledand maintained and, in turn, provide more uniform flow adjacent the sidedams.

Referring to FIG. 8, another alterative embodiment of the metal deliverynozzle is illustrated where the inner trough 14 of each delivery nozzlesegment 13 does not extend into the end portions 18 underneath thereservoir 24. This embodiment does not provide relatively uniform flowof molten metal into the cast pool 8 to the end portion 18 of thesegment 13. However, this embodiment may be desired because ofsimplicity in the making of the delivery nozzle 10.

Referring to FIG. 9, another alternative of the delivery nozzle 10 andsegments thereof is illustrated. Partitions 17 extend between side walls15 at spaced locations along each segment 13, and provide structuralsupport for the segment 13 of the delivery nozzle 10 when loaded withmolten metal during a casting campaign. Passages 16 are formed betweenthe side walls 15 and the inner trough 14 as shown in FIGS. 1 a and 1 b.Passages 16 extend between partitions 17 or between a partition 17 andthe end walls 18 or 19 along the length of the delivery nozzle segments13. Passages 16 extend to side outlets 20 at the bottom portion 21 ofthe segment 13. The configuration of the reservoir portion 24 with thefirst passages 22 and the second passages 23 is the same as describedabove with reference to FIGS. 1 a, 1 b, and 5.

Referring to FIG. 10, each delivery nozzle segment 13 is assembled intwo pieces, with one piece being the inner trough 14 and the bottomportion 21 as shown in FIG. 1 a. The other piece includes all of theother parts of the delivery nozzle segment 13 as described above withreference to FIGS. 1-5. The two pieces are assembled together by use ofceramic pins 32, which extend through holes on the side walls 15 andinto or through holes in the side portions of the inner trough 14. Theceramic pins provide structural support for the segments 13 and theassembled delivery nozzle 10 when the delivery nozzle 10 is loaded withmolten metal during a casting campaign. The configuration of thereservoir 24 with the first passages 22 and the second passages 23 isthe same as described above with reference to FIGS. 1 a, 1 b, and 5.

It should be understood that the above described apparatus and method ofcasting thin strip are the presently contemplated best modes ofembodying the invention. Other details in the assembly and operation ofthe casting method and metal delivery nozzle therefor is described byreference to pending application Ser. No. 12/403,876, filed Mar. 13,2009, which is incorporated herein by reference. It is to be understoodthat these and other embodiments may be made, and performed, within thescope of the following claims. In each embodiment of the deliverynozzle, the nozzle insert dissipates a substantial part of the kineticenergy built up in the molten metal by reason of movement through thedelivery system from the metal distributor to the delivery nozzle, andthe resistance to movement of the molten metal from the inner troughthrough the passages to the side outlets further reducing the kineticenergy in the molten metal from the molten metal before reaching thecasting pool. As a result, a more uniform and more quiescent flow ofmolten metal is provided to the casting pool for the formation of thecast strip.

While the principle and mode of operation of this invention have beenexplained and illustrated with regard to particular embodiments, it mustbe understood, however, that this invention may be practiced otherwisethan as specifically explained and illustrated without departing fromits spirit or scope.

1. A method of casting metal strip comprising: (a) assembling a pair ofcasting rolls laterally disposed to form a nip between them and betweenside dams adapted to maintain a molten metal pool supported by thecasting rolls, (b) assembling an elongated metal delivery nozzleextending along and above the nip with at least one segment having amain portion adapted to deliver molten metal in the casting pool alongthe metal delivery nozzle and an end portion adjacent side dams having areservoir portion having first and second passages adapted to delivermolten metal into a molten metal pool adjacent the side dams whileshells are forming on the casting rolls, the first passages adapted todeliver molten metal shallowly into the casting pool adjacent the sidedams and the second passages adapted to deliver molten metal deeper intothe casting pool than the first passages adjacent the side dams, (c)introducing molten metal through the elongated metal delivery nozzle toform a casting pool of molten metal supported on the casting rolls abovethe nip, and through the first and second passages in the reservoirportion in the end portions into the casting pool, and (d) counterrotating the casting rolls to deliver cast strip downwardly from thenip.
 2. The method of casting metal strip as claimed in claim 1 wherethe first and second passages of the reservoir portion are substantiallyparallel.
 3. The method of casting metal strip as claimed in claim 1where the first and second passages of the reservoir portion are between5 and 30 millimeters apart.
 4. The method of casting metal strip asclaimed in claim 1 where the first and second passages of the reservoirportion are shaped to control the velocity of molten metal through thepassages.
 5. The method of casting metal strip as claimed in claim 1where the reservoir portion in the end portion of each segment haslongitudinally extending weirs adjacent the side walls of the innertrough adapted to allow molten metal to flow over the weirs between thereservoir portion and the main portion.
 6. The method of casting metalstrip as claimed in claim 1 where dual first and second passages areprovided in each reservoir portion of the metal delivery nozzle.
 7. Themethod of casting metal strip as claimed in claim 6 where the first andsecond passages of the reservoir portion are substantially parallel. 8.The method of casting metal strip as claimed in claim 6 where the firstand second passages of the reservoir portion are between 5 and 30millimeters apart.
 9. The method of casting metal strip as claimed inclaim 6 where the first and second passages of the reservoir portion areshaped to control the velocity of molten metal through the passages. 10.The method of casting metal strip as claimed in claim 6 where thereservoir portion in the end portion of each segment has longitudinallyextending weirs adjacent the side walls of the inner trough adapted toallow molten metal to flow over the weirs between the reservoir portionand the main portion of the delivery nozzle.
 11. A metal deliveryapparatus for casting metal strip comprising at least one elongatedsegment having a main portion adapted to deliver molten metal in thecasting pool along the metal delivery nozzle and an end portion adjacentside dams having a reservoir portion having first and second passagesadapted to deliver molten metal into a molten metal pool adjacent theside dams while shells form on the casting rolls, the first passagesadapted to deliver molten metal shallowly into the casting pool adjacentthe side dams and the second passages adapted to deliver molten metaldeeper into the casting pool than the first passages adjacent the sidedams.
 12. The metal delivery apparatus for casting metal as claimed inclaim 11 where the first and second passages of the reservoir portionare substantially parallel.
 13. The metal delivery apparatus for castingmetal strip as claimed in claim 11 where the first and second passagesof the reservoir portion are between 5 and 30 millimeters apart.
 14. Themetal delivery apparatus for casting metal strip as claimed in claim 11where the first and second passages of the reservoir portion are shapedto control the velocity of molten metal through the passages.
 15. Themetal delivery apparatus for casting metal strip as claimed in claim 11where the reservoir portion in the end portion of each segment haslongitudinally extending weirs adjacent the side walls of the innertrough adapted to allow molten metal to flow over the weirs between thereservoir portion and the main portion of the metal delivery apparatus.16. The metal delivery apparatus for casting metal strip as claimed inclaim 11 where dual first and second passages are provided in eachreservoir portion of the metal delivery nozzle.
 17. The metal deliveryapparatus for casting metal strip as claimed in claim 16 where the firstand second passages of the reservoir portion are substantially parallel.18. The metal delivery apparatus for casting metal strip as claimed inclaim 16 where the first and second passages of the reservoir portionare between 5 and 30 millimeters apart.
 19. The metal delivery apparatusfor casting metal strip as claimed in claim 16 where the first andsecond passages of the reservoir portion are shaped to control thevelocity of molten metal through the passages.
 20. The metal deliveryapparatus for casting metal strip as claimed in claim 16 where thereservoir portion in the end portion of each segment has longitudinallyextending weirs adjacent the side walls of the inner trough adapted toallow molten metal to flow over the weirs between the reservoir portionand the main portion of the delivery apparatus.